1. Field of the Invention
The present invention relates to a multi-core optical amplifying fiber device and a multi-core optical fiber amplifier using this.
2. Description of the Related Art
A multi-core optical fiber is studied in which a plurality of core portions are formed in one cladding portion. This multi-core optical fiber is used for the purpose of conducting a so-called Space Division Multiplexing communication in which signal lights are propagated in the plurality of core portions although the multi-core optical fiber is of an outer diameter similar to that of a single-core optical fiber in which a core portion is formed in a cladding portion. By using Space Division Multiplexing communication as such, it is possible to increase transmission capacity per one optical fiber as a transmission path. When configuring a multi-core optical fiber optical transmission system using the multi-core optical fiber as such, a signal light amplifier for compensating for transmission loss in the transmission path is necessary similarly to using a single-core optical fiber as a transmission path. Several optical amplifiers have been proposed for amplifying signal lights transmitted through the plurality of core portions in a multi-core optical fiber (see K. S. Abedin et al., “Amplification and noise properties of an erbium doped multicore fiber amplifier”, Optics Express, vol. 19, no. 17, pp. 16715, 2011, Y. Mimura et al., “Batch Multicore Amplification with Cladding-Pumped Multicore EDF”, in Proc.ECOC2012, Tu.4.F.1, (2012), and Y. Tsuchida et al., “Simultaneous 7-Core Pumped Amplification in Multicore EDF through Fibre Based Fan-In/Out,” in Proc.ECOC2012, Tu. 4. F. 2 (2012)).
Among them, a multi-core optical fiber amplifier using a rare-earth-doped multi-core optical fiber having a plurality of cores which are doped with rare-earth metal as an amplification medium is a technology of which introduction to an optical transmission system is under investigation due to superior affinity with a multi-core optical fiber constituting the multi-core optical fiber transmission path. Similarly to the conventional optical transmission system, a multi-core optical fiber optical transmission system as well can use wavelength division multiplexing (WDM) transmission technology by which a plurality of signal lights having different wavelengths are multiplexed to be transmitted.